Stabilizing unintentional muscle movements

ABSTRACT

A system and method for stabilizing unintentional muscle movements are disclosed. In a first aspect, a non-contact sensing system comprises a stabilization unit, at least one non-contact position sensor coupled to the stabilization unit, and a processing unit coupled to the at least one non-contact position sensor, wherein the processing unit transmits motion commands to the stabilization unit to cancel unintentional muscle movements. In a second aspect, the method comprises a processing unit of a non-contact sensing system receiving position data of a stabilization unit that is detected by at least one non-contact position sensor and filtering the position data to identify the unintentional muscle movements. The method includes modeling the position data to create a system model and determining motor commands based upon the system model to cancel the unintentional muscle movements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/250,000, Sep. 30, 2011, entitled “SYSTEM AND METHOD FORSTABILIZING UNINTENTIONAL MUSCLE MOVEMENTS,” and claims the benefit ofU.S. Provisional Patent Application No. 61/777,855, filed on Mar. 12,2013, entitled “WIRELESS SENSING AND CONTROL,” all of which areincorporated herein by reference in their entireties.

This invention was made with government support under Grant No. NS070438awarded by National Institutes of Health (NIH). The government hascertain rights in the invention.

FIELD OF THE INVENTION

The present invention relates generally to unintentional musclemovements, and more particularly, to stabilizing these unintentionalmuscle movements.

BACKGROUND

Unintentional muscle movements of the human body, or human tremors, canoccur in individuals suffering from neurological motion disordersincluding but not limited to Parkinson's Disease (PD) and EssentialTremor (ET) and healthy individuals in stressful situations. Due to thedebilitating muscle movements associated with this disease, individualswith ET have difficulty in performing many daily functions such aseating and drinking. As a result, these individuals often suffer fromsocial isolation, depression/anxiety, and an overall reduced HealthRelated Quality of Life (HRQoL).

For individuals suffering from unintentional muscle movements, a varietyof conventional treatment options exist. Pharmacological treatments varyin effectiveness, can lead to severe side effects and are unable to slowor stop disease progression. Surgical procedures, such as Thalamotomyand thalamic Deep Brain Stimulation (DBS) can be expensive, dangerous,and limited in availability. Non-invasive solutions, such as physicallygrounded tremor suppression devices, physically force a person's tremorto cease but require complex and costly structures, cause userdiscomfort and cannot differentiate between intended and unintendedmovements.

These issues limit the adoption of these treatments to selectneurological motion disorder cases. Thus, for the majority ofindividuals that suffer from human tremor, there is a strong need for anon-invasive solution that overcomes the above issues. The presentinvention addresses such a need.

SUMMARY OF THE INVENTION

A system and method for stabilizing unintentional muscle movements aredisclosed. In a first aspect, a non-contact sensing system comprises astabilization unit, at least one non-contact position sensor coupled tothe stabilization unit, and a processing unit coupled to the at leastone non-contact position sensor, wherein the processing unit transmitsmotion commands to the stabilization unit to cancel unintentional musclemovements.

In a second aspect, the method comprises a processing unit of anon-contact sensing system receiving position data of a stabilizationunit that is detected by at least one non-contact position sensor andfiltering the position data to identify the unintentional musclemovements. The method includes modeling the position data to create asystem model and determining motor commands based upon the system modelto cancel the unintentional muscle movements.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate several embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. One of ordinary skill in the art readilyrecognizes that the particular embodiments illustrated in the drawingsare merely exemplary, and are not intended to limit the scope of thepresent invention.

FIG. 1 illustrates a conventional handheld system that detects andcompensates for unintentional muscle movements.

FIG. 2 illustrates a system that detects and compensates forunintentional muscle movements in accordance with an embodiment.

FIG. 3 illustrates a motion-generating mechanism in accordance with anembodiment.

FIG. 4 illustrates an analytical model in accordance with an embodiment.

FIG. 5 illustrates a system diagram of the control system in accordancewith an embodiment.

FIG. 6 illustrates a non-contact sensing scheme in accordance with anembodiment.

FIG. 7 illustrates a flowchart of a signal processing algorithmprocessed by a processing unit of a non-contact sensing scheme inaccordance with an embodiment.

DETAILED DESCRIPTION

The present invention relates generally to unintentional musclemovements, and more particularly, to stabilizing these unintentionalmuscle movements. The following description is presented to enable oneof ordinary skill in the art to make and use the invention and isprovided in the context of a patent application and its requirements.Various modifications to the preferred embodiment and the genericprinciples and features described herein will be readily apparent tothose skilled in the art. Thus, the present invention is not intended tobe limited to the embodiments shown but is to be accorded the widestscope consistent with the principles and features described herein.

FIG. 1 illustrates a conventional handheld system 100 that detects andcompensates for unintentional muscle movements. The handheld system 100includes a base 102, a gripping element 106 coupled to the base 102, andan object 116 (in this embodiment, a spoon) coupled to the grippingelement 106. The base 102 houses a stabilizing assembly using shapememory alloy (SMA) wires 104, a power source 108 coupled to thestabilizing assembly 104, a single sensor 110 coupled to the powersource 108, a controller 112 coupled to the single sensor 110, and ashaft 114 coupled to the stabilizing assembly 104. SMA wires are alloywires that, after deformation, undergo a phase change to return to theiroriginal cold-forged shape after sufficient heat is applied. The SMAwires utilized in the stabilizing assembly 104 are heated by the powersource 108 to trigger this phase change.

In the handheld system 100, the single sensor 110 is located within thebase 102 to detect a user's motion and then the sensor 110 commands thestabilizing assembly using SMA wires 104 to produce a canceling motion.Unfortunately, several problems exist preventing the immediate use ofSMA wires. For example. SMA wires have not been proven for long-term,reliable use and also require significant complexity and cost to providesufficient motion to cancel large amplitude (1-4 cm) disabling tremors.

In addition, because the single sensor 110 is located within the base102, the use of the device is restricted to an object 116 that has apre-determined length and weight that must be pre-programmed into thecontroller 112. Deviations from this pre-determined length or weightwill result in control instabilities and a reduction in the efficacy ofthe motion cancellation.

A system and method in accordance with the present invention addressesthese drawbacks. The system and method include an inertial sensor placedalong an attachment arm and a motion-generating mechanism that does notutilize SMA wires. In so doing, the motion of the varying stabilizedobjects can be directly measured and there is no need forpre-programming the pre-determined lengths and weights into thecontroller. Additionally, a higher performing handheld form-factorsolution is achieved and the size and cost of the active cancellationsystem is further reduced. To describe the features of the presentinvention in more detail, refer now to the following description inconjunction with the accompanying Figures.

FIG. 2 illustrates a system 200 that detects and compensates forunintentional muscle movements in accordance with an embodiment. Thesystem 200 includes a housing 202. The housing 202 includes a subsystem204. The system 200 also includes an attachment arm 206 coupled to thehousing 202. At least one inertial sensor 208 is placed along theattachment arm 206. The attachment arm 206 is configured to accept anobject 210 thereto. The subsystem 204 further includes a portable powersource 212, a motion-generating mechanism 214, a controller 216, acontrol system 218, and at least one distributed motion sensor 220.

The attachment arm 206 can receive the object 210 in a variety of waysincluding but not limited to a friction, snap, or other form of lockingmechanism. The portable power source 212 may utilize a variety ofoptions including but not limited to a rechargeable battery and a solarpanel. The operation and details of the elements of the at least oneinertial sensor 208, at least one distributed motion sensor 220,motion-generating mechanism 214, controller 216, and control system 218will be described in more detail hereinafter.

The at least one inertial sensor 208 and the at least one distributedmotion sensor 220 detect unintentional muscle movements and measuresignals related to these unintentional muscle movements that are createdwhen a user adversely affects motion of the object 210. These sensorsalso detect the motion of the stabilized output relative to the housing202. The control system 218 sends voltage commands in response to themeasured signals to the motion-generating mechanism 214 through thecontroller 216 to cancel the user's tremors or unintentional musclemovements. This cancellation maintains and stabilizes a position of theobject 210, keeping it centered relative to the housing 202.

The present invention may utilize various implementations of thecontroller 216, at least one inertial sensor 208, at least onedistributed motion sensor 220, and control system 218. In oneembodiment, the controller 216 comprises an electrical system capable ofproducing an electrical response from sensor inputs such as aprogrammable microcontroller or a field-programmable gate array (FPGA).In one embodiment, the controller 216 comprises an 8-bit ATMEGA8Aprogrammable microcontroller manufactured by Atmel due to its overalllow-cost, low-power consumption and ability to be utilized inhigh-volume applications.

In one embodiment, the at least one inertial sensor 208 is a sensorincluding but not limited to an accelerometer, gyroscope, or combinationof the two. In one embodiment, the at least one distributed motionsensor 220 is a contactless position sensor including but not limited toa hall-effect magnetic sensor. In one embodiment, the control system 218is a closed-loop control system.

The closed-loop control system senses motion and acceleration at variouspoints in the system 200 and feeds detailed information into a controlalgorithm that moves the motion-generating mechanism 214 appropriatelyto cancel the net effect of a user's unintentional muscle movements andthus stabilize the position of the object 210. The operation and detailsof the elements of the control system and control algorithm will bedescribed in more detail hereinafter.

Also, one of ordinary skill in the art readily recognizes that a systemand method in accordance with the present invention may utilize avariety of objects including but not limited to kitchen utensils such asspoons and forks, grooming utensils such as make-up applicators, andvarious tools such as manufacturing, surgical and military tools. Thus,the system and method will be useful in not only improving the qualityof life for the multitudes of individuals suffering from neurologicalmotion disorders, but also in assisting in a variety of applicationswhere physiological tremor is an issue including but not limited tomanufacturing, surgical and military applications.

The system 200 stabilizes the object 210's position about a neutralposition (selected to be θ=0) using the at least one inertial sensor208. To achieve this, the position of the object 210 must be sensedalong with the angle θ. For this position sensing, the at least oneinertial sensor 208 is placed along the attachment arm 206 and is usedto measure the absolute motion of the object 210 while providing lownoise and sufficient sensitivity for the application. The direct sensorplacement of the at least one inertial sensor 208 along the attachmentarm 206 gives a unique advantage to the system 200 as it is extremelyrobust and does not rely on inverse kinematics/dynamics which may changedepending on usage. Thus, as aforementioned, a variety of objects can beused as the object 210 without the need to pre-determine and pre-programthe length and weight of the object 210 into the controller 216.

The at least one distributed motion sensor 220 is located within thehousing 202 which is located at the base of the system 200. The at leastone distributed motion sensor 220 measures the relative motion of theattachment arm 206 relative to the housing 202, wherein the object 210is kept at a center position relative to the housing 202. In oneembodiment, the at least one distributed motion sensor 220 is at leastone custom contactless hall-effect position sensor that provides angularfeedback for the control system 218 and relies on a changing magneticfield that is dependent on the actuation angle.

The changing magnetic field is detected by a strategically placedintegrated circuit (IC) located within the at least one distributedmotion sensor 220, whose analog output is read by the controller 216,providing a completely non-contact angular detection that is capable ofwithstanding a large number of cycles. The at least one distributedmotion sensor 220, with its contactless sensing methods, providessignificantly enhanced reliability over traditional direct-contactsensing methods such as potentiometers that wear over time.

Proper actuator operation is also a key to the overall operation of thesystem 200. Actuator options include SMA wires, piezoelectrics, linearvoice-coils and coreless motors. However, SMA wires, piezoelectrics andlinear voice-coils suffer from various fundamental problems. Forexample, as noted in the “Fatigue Life characterization of shape memoryalloys undergoing thermomechanical cyclic loading” article within the“Smart Structures and Materials” publication, SMA wires suffer fromreliability issues where failures occur after 10⁴ to 10⁵ cycles withstrain amplitudes between 8.3% and 4.4%, which would amount to only 200days usage time. Piezoelectrics, while capable of longer cycle times,are fragile and expensive. In addition, they require high operatingvoltages and thus require relatively large and expensive driveelectronics. Linear voice-coils operate at lower voltages but sufferfrom low force outputs and high costs.

The present invention addresses these drawbacks by using a combinationof coreless micro-motors and miniature gear-reduction systems coupled tothe coreless micro-motors using a coupling mechanism for themotion-generating mechanism 214. In volume, coreless micro-motors areinexpensive and provide up to 1000 hours of operation time. Significantforce of up to 10 newtons (N) can also be produced with these corelessmicro-motors at the required tremor frequency of 0-5 hertz (Hz) throughthe use of a low-cost miniature gear-reduction system, with a totalweight of only 6.5 grams (g). Furthermore, the power drawn from thistechnology is extremely low, estimated at 0.5 watts (W).

The coreless micro-motors are not only capable of holding a maximum loadof 50 g while requiring 0.3 W of power, but are also capable of holdingthe lighter average filled tablespoon load of 14 g while requiring asignificantly lower 0.06 W of power. Thus, the coreless micro-motors aresuitable in generating the required forces for the system 200.

FIG. 3 illustrates a motion-generating mechanism 300 in accordance withan embodiment. The motion-generating mechanism 300 is an embodiment ofthe motion-generating mechanism 214 of the system 200. Themotion-generating mechanism 300 includes a first miniaturegear-reduction system coupled to a first coreless micro-motor 302 and asecond miniature gear-reduction system coupled to a second corelessmicro-motor 304. At least one inertial sensor 308 is placed along anattachment arm 306. The attachment arm 306 is configured to accept anobject 310 thereto.

The first coreless micro-motor is capable of producing rotary motion inthe horizontal (x) direction. This rotary motion is imparted to thesecond coreless micro-motor through a rigid connection that is supportedby a horizontal bearing. The second coreless micro-motor is capable ofproducing motion in the vertical (y) direction. This motion from thesecond coreless micro-motor is supported by a vertical bearing.

A coupling mechanism is used to combine the horizontal and verticalmotions of the two separate coreless micro-motor/miniaturegear-reduction systems 302 and 304. This combination results in abi-directional circular motion of the object 310 (in this embodiment, aspoon). In one embodiment, the coupling mechanisms include but are notlimited to sliding bearing mechanisms, gimbal structures, and bellowsstructures.

In the motion-generating mechanism 300, two degrees of freedom aregenerated from the two separate coreless micro-motor/miniaturegear-reduction systems 302 and 304. Additional degrees of freedom (e.g.,a third in the z-direction) can be added to the motion-generatingmechanism 300 by adding motion to the output of the first corelessmicro-motor or the output of the second coreless micro-motor.

To assist with the development of the control system type and parametervalues, an analytical model of the system 200's properties was created.FIG. 4 illustrates an analytical model 400 in accordance with anembodiment. The analytical model 400 includes a handle 402, an actuator404, an angular sensor 406, an attachment arm 408, an object 410, and aninertial sensor 412. The analytical model 400 was created withsufficient complexity to capture the dynamics of the system 200 and itsresponse when synthesized with a closed-loop control system.

While the system 200 is designed to provide stabilization in multipledirections (e.g., vertical, horizontal, and the z-direction), analysisand modeling in only one direction is required because the motionoutputs were symmetric and completely decoupled from one another. Thus,results from the vertical direction are directly applicable to otherdirections such as but not limited to the horizontal direction, assuminggravitational effects are negligible.

In the analytical model 400, the object 410 moves in the vertical ydirection. The tremor disturbance or unintentional muscle movement(coordinate x) is assumed to act directly on the handle 402. The object410 requiring stabilization (distance l from the base) moves a verticaldistance y. This distance is related to the base coordinate x throughthe transformation,y=x+lθ,  (1)where small angles are assumed. The actuator 404 is capable of movingthe object 410 through the angle θ based on the controller's voltageoutput. The output torque of the actuator 404's coreless motor T isproportional to its armature current i through the relationshipT=K _(t) i,  (2)where K_(t) is a constant. Similarly, the back electromotive force(emf), e is related to the coreless motor's rotational velocity throughe=k _(e){dot over (θ)}  (3)

For simplicity, and based on the manufacturer's specifications, K_(e)and K_(t) are approximately equal and are therefore set to a constant k.With the actuator 404's model Equations 2 and 3, the system equationscan be constructed through a combination of Newton's and Kirchhoff'slaws. Through a moment balance the dynamic equation is constructed as

$\begin{matrix}{{{I\;\overset{¨}{\theta}} + {\frac{m\; l}{2}\overset{¨}{x}}} = {k\;{i.}}} & (4)\end{matrix}$The second system equation is constructed as

$\begin{matrix}{{{J\frac{\mathbb{d}i}{\mathbb{d}t}} + {Ri}} = {V - {k\;\overset{.}{\theta}}}} & (5)\end{matrix}$where V is the input voltage/command signal from the controller, J isthe inductance of the actuator 404, and R is the internal resistance ofthe actuator 404.

The system 200 acts as a low-pass filter because it is designed tocancel high-frequency tremor disturbances/unintentional muscle movementswhile retaining low-frequency intended motions. Thus, the system 200 canbe modeled as a transfer function, where an input amplitude X (tremordisturbance) is entered into the system 200, and an output Y (motion ofthe stabilized object) is observed and controlled.

For further analysis on tremor cancellation and to assist in controllerdesign, the system Equations 4 and 5 were transformed into the frequencydomain and manipulated to produce the desired transfer function. Usingthe coordinate transformation Equation 1 and performing a Laplacetransform, Equations 4 and 5 were modified to produce

$\begin{matrix}{{{{\frac{I}{l}{s^{2}\left( {{Y(s)} - {X(s)}} \right)}} + {\frac{m\; l}{2}s^{2}{X(s)}}} = {k\;{I(s)}}}{and}} & (6) \\{{{J\;{{sI}(s)}} + {{RI}(s)}} = {V - {\frac{Ks}{l}{\left( {{Y(s)} - {X(s)}} \right).}}}} & (7)\end{matrix}$

Solving Equation 7 for l(s) and substituting the result into Equation 6produces a single equation

$\begin{matrix}{{{\frac{I}{l}{s^{2}\left( {{Y(s)} - {X(s)}} \right)}} + {\frac{m\; l}{2}s^{2}{X(s)}}} = {{k\left( \frac{V - {\frac{Ks}{l}\left( {{Y(s)} - {X(s)}} \right)}}{{J\; s} + R} \right)}.}} & (8)\end{matrix}$The remaining input in Equation 8 is V, which is the inputvoltage/command signal from the controller. This signal was designed tobe simple in nature to minimize computational requirements and thussignificantly reduce the cost and power consumption of the necessarymicrocontroller.

FIG. 5 illustrates a system diagram 500 of the control system 218 inaccordance with an embodiment. The system diagram 500 includes anunintentional muscle movement 502, a stabilized object 504, accelerationsignals 506, an adaptive acceleration set-point 508, a positionset-point 510, a control algorithm 512, a voltage command output 514, amotion-generating mechanism 516, and position signals 518.

An unintentional muscle movement 502 by a user that adversely affectsthe motion of the stabilized object 504 is detected. Position signals518 relative to the housing are measured by the at least one contactlessposition angular sensor and then are compared to the position set-point510 that is stored in the microcontroller's memory (e.g., ElectricallyErasable Programmable Read-Only Memory (EEPROM)). The position set-point510 is the neutral position of the stabilized object 504 and isinitially calibrated when the system 200 is first activated. Thiscomparison results in a first input signal.

Acceleration signals 506 are measured by the at least one inertialsensor and then are compared to an adaptive acceleration set-point 508.The adaptive acceleration set-point 508 removes the effects of slowchanges in the gravity field due to the changing orientation of thedevice. The adaptive acceleration set-point 508 can be implementedthrough the use of a median filter, low-pass filter, or otherdigital/analog filter capable of removing low frequencies from a signal.This comparison results in a second input signal.

The control algorithm 512 processes the first and second input signalsand sends an appropriate voltage command output 514 to themotion-generating mechanism 516 in each controlled direction to activelycancel the user's unintentional muscle movement and maintain thestabilized object 504.

Based on these two input signals (acceleration signal and angle θ), acontrol law must be constructed for the control algorithm 512. One ofordinary skill in the art readily recognizes that a system and method inaccordance with the present invention may utilize a variety of differentcontrol laws that provide tremor disturbance cancellation while ensuringstability of the object and that would be within the spirit and scope ofthe present invention.

For example, a control law can be derived by applying proportional andderivative gains to the angle θ along with the acceleration signalresulting inV=K ₁ θ−K ₂ ÿ+K3{dot over (θ)}.  (9)

In this example, the feedback on the acceleration term provides thedesired low-pass filtering properties. In the exemplified control law(Equation 9), the proportional feedback on the angle θ is applied toallow the device to mimic the function of conventional implements. Thisis achieved by creating “stiffness” in the angular direction to allowthe device to support various loads and while remaining in the neutralposition during the inactive state. Derivative control on the angularinput was selected for stability, particularly to dampen any resonancesintroduced by the proportional feedback on θ. The exemplified controllaw is both effective and computationally simple.

This allows the control algorithm 512 to be implemented in the highlycompact, low-power, and low-cost microcontrollers of the system 200.Substituting the exemplified control law (Equation 9) into V in Equation8 and expanding the terms allows Equation 8 to be expressed as thefollowing transfer function

$\begin{matrix}{\frac{Y(s)}{X(s)} = \frac{n}{d}} & (10)\end{matrix}$where the numerator isn=(2ILJ ² −mL ³ J ²)s ⁴+(4ILJR−2mL ³ JR)s ³+(2K ² LJ+2K ₃ KLJ−mL ³ R²+2ILR ²)s ²+(2K ² LR+2K ₁ KLJ+2K ₃ KLR)s+2K ₁ KLR  (11)and the denominator isd=(2ILJ ²)s ⁴+(2K ₂ KL ² J+4ILJR)s ³+(2K ² LJ+2K ₂ KL ² R+2K ₃ KLJ+2ILR²)s ²+(2K ² LR+2K ₁ KLJ+2K ₃ KLR)s+2K ₁ KLR.  (12)

To reject unintentional muscle movements while retaining intendedmotions, the parameters of the exemplified control law (Equation 9) areoptimized through numerical simulation. For example, this optimizationminimizes the average displacement magnitude of the stabilized object504 (Y, Equation 10) over the unintentional muscle movement frequencyrange of 3-7 Hz, while varying the controller gains K₁, K₂, K₃. Further,in this example, the constraints are defined such that low-frequencymotions in the intended motion frequency range of 0-1 Hz are unaffectedand stability is mathematically ensured. The average phase lag is alsoconstrained to be less than 15 degrees from 0-1 Hz, which is assumed tobe unnoticeable to the user.

For the optimization, computational functions are written to interactwith the trust-region reflective optimization algorithm fmincon inMatlab. The algorithm is run to provide a final solution,K=[121,366,154], which is used for the controller 216 in the system 200.The function has a minimum value of 0.15, which means that the system200 is capable of filtering on average 80% of the input tremordisturbances/unintentional muscle movements in the frequency range of3-7 Hz.

Additional sensing and processing schemes can be utilized to obtainactive cancellation of the unintentional muscle movements. FIG. 6illustrates a non-contact sensing system 600 in accordance with anembodiment. The non-contact sensing system 600 includes a stabilizationunit 602 that comprises a stabilized implement portion 602 a and a baseportion 602 b. The at least one non-contact position sensor 604 detectsposition data of the stabilization unit 602 and transmits the positiondata to the processing unit 606 which determines proper controlmechanisms to cancel out the unintentional muscle movements. The propercontrol mechanisms are transmitted back to the stabilization unit 602via a wireless link 608. In one embodiment, the transmission occurs viaa wired link between the processing unit 606 and the stabilization unit602.

The at least one non-contact position sensor 604 detects the position ofmultiple points along both the stabilized implement portion 602 a andthe base portion 602 b in a three-dimensional coordinate system (e.g. x,y, and z coordinates). In one embodiment, the at least one non-contactposition sensor 604 is an optical camera such as any of an infrared (IR)camera, a visible light camera, and a stereo camera. In anotherembodiment, the at least one non-contact position sensor 604 is any of alaser displacement sensor, an ultrasonic sensor.

In FIG. 6, position data of the stabilization unit 602 is extracted fromthe non-contact position sensor 604 and transmitted to the processingunit 606. In one embodiment, the processing unit 606 comprises amicroprocessor that is capable of running and processing controlalgorithms associated with analyzing the received position data. Inanother embodiment, the processing unit 606 is any of a personalcomputer device, a mobile phone, and a custom signal processor. Afterreceiving the position data and processing control algorithms, theprocessing unit 606 transmits actuator commands via the wireless link608 to the base portion 602 b of the stabilization unit 602.

In one embodiment, the base portion 602 b includes embedded sensorsincluding but not limited to accelerometers and gyro sensors forfeedback control and the cancellation of unintentional muscle movements.In another embodiment, the base portion 602 b switches from utilizingdata detected from the embedded sensors to utilizing data detected fromthe at least one non-contact position sensor 604 when available. Inanother embodiment, the base portion 602 b combines data detected fromthe embedded sensors and the at least one non-contact position sensor604 to optimize the cancellation of unintentional muscle movements.

Referring to FIG. 6 and FIG. 7 together, FIG. 7 illustrates a flowchartof a signal processing algorithm 700 processed by the processing unit606 of the non-contact sensing scheme in accordance with an embodiment.The signal processing algorithm 700 receives position data of thestabilized object that has been detected by a non-contact positionsensor, via step 702, and filters the position data to identify tremorand unintentional muscle movements, via step 704. The signal processingalgorithm further models the identified tremor, via step 706, andproduces motor commands that will cancel out the identified tremor, viastep 708.

In FIG. 7, the signal processing algorithm 700 is utilized by theprocessing unit 606 to detect position data of both the stabilizedimplement portion 602 a and the base portion 602 b of the stabilizationunit 602 and extract the unwanted/unintentional tremor. In oneembodiment, the processing unit 606 utilizes any of low pass filters,weighted-frequency Fourier linear combiners, and notch filters toextract the unwanted tremor. A system model is employed to calculatemotor commands necessary to cancel the motion of the unwanted tremor andthe motor commands are transmitted via either a wireless or wired linkto the stabilization unit 602. The remote, wireless sensing, processing,and controlling makes the non-contact sensing scheme compact andflexible for a variety of applications.

As above described, the system and method in accordance with the presentinvention allow for a highly compact active cancellation approach thatseeks to accommodate a user's tremor by allowing it to exist whilecancelling its effects and stabilizing the position of the object. Byimplementing a motion-generating mechanism to provide the necessaryforces and displacements for tremor cancellation and a control systemand sensor topology to control this motion-generating mechanism, thesystem and method in accordance with the present invention achieve amore robust handheld form-factor with a significantly reduced size andcost.

Although the present invention has been described in accordance with theembodiments shown, one of ordinary skill in the art will readilyrecognize that there could be variations to the embodiments and thosevariations would be within the spirit and scope of the presentinvention. Accordingly, many modifications may be made by one ofordinary skill in the art without departing from the spirit and scope ofthe appended claims.

What is claimed is:
 1. A human tremor compensation system, comprising: astabilization unit including: a base portion adapted to be held in auser's hand and having a motion-generating mechanism in an interior ofthe base portion, wherein the motion-generating mechanism includes anactuator; and an implement portion coupled by an attachment arm to themotion-generating mechanism, wherein the motion-generating mechanism iscoupled to move the attachment arm and the implement portion relative tothe base portion; at least one remote non-contact position sensorexternal to and not in physical contact with the stabilization unit,wherein the non-contact position sensor can sense a position in athree-dimensional coordinate system of at least the base portion; and aprocessing unit coupled to the at least one remote non-contact positionsensor, wherein the processing unit is disposed external to thestabilization unit and wirelessly transmits motion commands to themotion-generating mechanism within the base portion of the stabilizationunit to move the implement portion relative to the base portion todynamically cancel the user's unintentional muscle movements.
 2. Thehuman tremor compensation system of claim 1, wherein the at least onenon-contact position sensor is any of an infrared (IR) optical camera, avisible light camera, a stereo camera, a laser displacement sensor, andan ultrasonic sensor.
 3. The human tremor compensation system of claim1, wherein the processing unit receives the position data from the atleast one remote non-contact position sensor and calculates the motioncommands based upon the position data.
 4. The human tremor compensationsystem of claim 3, wherein the processing unit calculates the motioncommands utilizing a signal processing algorithm.
 5. The human tremorcompensation system of claim 4, wherein the signal processing algorithmis developed utilizing any of low pass filters, weighted-frequencyFourier linear combiners, and notch filters.
 6. The human tremorcompensation system of claim 4, wherein the signal processing algorithmfurther comprises position data filtration, tremor identification,system modeling, and actuator command generation.
 7. The human tremorcompensation system of claim 1, wherein the base portion of thestabilization unit switches between utilizing embedded sensor data andutilizing position data detected by the at least one remote non-contactposition sensor.
 8. The human tremor compensation system of claim 1,wherein: the base portion includes a housing having therein a subsystemthat comprises a power source coupled to the motion-generatingmechanism, a controller coupled to the motion-generating mechanism, acontrol system coupled to the controller, and at least one first sensorcoupled to the control system; and wherein at least one second sensor isplaced along the attachment arm, wherein the attachment arm isconfigured to receive an implement, and wherein in response to theuser's unintentional muscle movement the subsystem stabilizes a positionof the implement.
 9. The human tremor compensation system of claim 1,further comprising one or more embedded sensors disposed with thestabilization unit, and wherein the base portion of the stabilizationunit is configured to switch between utilizing the position data of oneor more embedded sensors of the stabilization unit to control themotion-generating mechanism and utilizing the motion commands wirelesslycommunicated from the processing unit.
 10. A human tremor compensationsystem, comprising: a stabilization unit including: a base portionadapted to be held in a user's hand and having a motion-generatingmechanism in an interior of the base portion, wherein themotion-generating mechanism includes an actuator; and an implementportion coupled by an attachment arm to the motion-generating mechanism,wherein the motion-generating mechanism is coupled to move theattachment arm and the implement portion ‘1relative to the base portion;at least one remote non-contact position sensor external to and not inphysical contact with the stabilization unit, wherein the non-contactposition sensor can sense the position in a three-dimensional coordinatesystem of at least the base portion; a processing unit disposed externalto the base portion and in communication with the stabilization unit viaa wireless link, wherein the processing unit is further coupled to theat least one remote non-contact position sensor and transmits motioncommands to the motion-generating mechanism within the base portion ofthe stabilization unit via the wireless link to move the implementportion relative to the base portion to dynamically cancel the user'sunintentional muscle movements.
 11. The human tremor compensation systemof claim 10, wherein: the base portion includes a housing having thereina subsystem that comprises a power source coupled to themotion-generating mechanism, a controller coupled to themotion-generating mechanism, a control system coupled to the controller,and at least one first sensor coupled to the control system; and whereinat least one second sensor is placed along the attachment arm, whereinthe attachment arm is configured to receive an implement, and wherein inresponse to the user's unintentional muscle movement the subsystemstabilizes a position of the implement.
 12. The human tremorcompensation system of claim 10, further comprising one or more embeddedsensors disposed with the stabilization unit, and wherein the baseportion of the stabilization unit is configured to switch betweenutilizing position data of the one or more embedded sensors of thestabilization unit to control the motion-generating mechanism andutilizing the motion commands wirelessly communicated from theprocessing unit.